Microsoft recommends the use of the INFORMATION_SCHEMA views in lieu of system tables, as they reserve the right to change said tables, while the views remain relatively static.

select TABLE_SCHEMA, TABLE_NAME, COLUMN_NAME, DATA_TYPE, CHARACTER_MAXIMUM_LENGTH

from INFORMATION_SCHEMA.COLUMNS

where DATA_TYPE in ('text','ntext','image','xml')

OR (DATA_TYPE in ('varchar','nvarchar','varbinary') AND CHARACTER_MAXIMUM_LENGTH = -1)